As a prior apparatus for identifying persons by their face images there is one described in Japanese Pat. laid-open Publication No. Sho 63-177273. The composition of that apparatus is described in the following.
FIG. 15 shows a block diagram showing a composition of the prior apparatus for identifying persons by their face images. In the Figure, 21 is an image input section that inputs a face image, 22 is a feature-points extracting section comprising an analog-to-digital converter, a central processor, and a memory, 23 is a personal database section that records people's feature points on cards or the like, 24 is a judgment section that uses the feature-points information of above feature-points extracting section 22 and the feature-points information of personal database section 23 to detect their difference and identifies the person having that face image as the person of personal database 23 based on the test whether the difference is greater than a threshold value or not.
The above prior technology extracts, in feature-points extracting section 22, feature points of a person's face image input from image input section 21 and detects, in judgment section 24, the differences between these feature points and the feature points of a face image registered in personal database section 23, and identifies the person based on the amount of the difference. In this case, if the sizes of the two images are different, or if their photographing angles are different, then the differences in the feature points become great, so that even the same person is identified as a different person. In order to avoid such a situation, it was necessary to fix the distance between the image input section and a photographed person and to make him or her face turned straight toward the front. However, this method of inputting a face image imposes a burden on the photographed person, and no matter how hard the person tries to turn straight to the front, a slight rotation and inclination are inevitable, so that it was difficult to obtain an image exactly facing the front.
The basic object of the present invention is to provide an apparatus for identifying persons having high discriminating power.
Another object of the present invention is to provide an apparatus for identifying persons that performs identification with high accuracy against minor fluctuations of photographing conditions such as illumination conditions and the position of the face.